For example, there is a telescopic device for use in a stepladder support comprising a pair of telescoping bodies each comprising an outer casing and an insertion element which is telescopically inserted in the outer casing, and has its tip made capable of placement on a ground surface. In this construction, the outer casings of the telescoping bodies are coupled in spaced relation to each other via rung members, and, each outer casing is provided with a locking mechanism for securely holding the insertion element in telescoped position, and an operating member for unlocking the locking mechanism, and also, in between the paired operating members, there is provided operating means for simultaneous manual operation of the paired operating members.
In a conventional telescopic device of this type, as disclosed in Patent Literature 1, a conducting element such as a wire is coupled to an unlocking lever (operating member) of one locking mechanism, is passed through the interior of a tube, is passed through the interior of a flexible operating lever accommodated at the back side of a top plate, is passed through another tube, and is coupled to an operating member of the other opposed locking mechanism, and, the operating lever accommodated at the back side of the top plate of a stepladder constitutes the operating means for simultaneous manual operation of the paired operating members. A user carries out simultaneous unlocking operation of the paired locking mechanisms standing up while holding the stepladder with his/her hands.
Moreover, in such a construction as disclosed in Patent Literature 2, in order for a locking mechanism mounted at a lower part of a support to be locked and unlocked from above the support, the locking mechanism is disposed inside an insertion element, and also a long operating member for operation of the locking mechanism is disposed inside the insertion element.
Furthermore, in such a construction as disclosed in Patent Literature 3, a locking mechanism mounted at an outer casing comprises: a locking member for locking an insertion element; a handle; a pivotal portion disposed at one end of the handle for supporting the locking member, the pivotal portion being piercingly supported in a pair of side walls of a support frame for axial movement; and a latching portion disposed at the other end of the handle for rocking the locking member. In this construction, the handle is supported for movement in a direction perpendicular to a rocking direction relative to the support frame, and, the support frame has formed in its side wall a latching hole which receives the latching portion. By operating the handle to move so that the latching portion is fitted in the latching hole during the time the insertion element is locked by the locking member, it is possible to restrain the handle, the locking member, and their included components against rocking motion, and thereby prevent the locking member from rocking for disengagement.